x = linspace(-5, 5);
% 原函数
plot(x,1./(1+x.^2),'k');
% n = 2
hold on;
plot(x,1 + -0.0384615*x.^2,'r');
% n = 4
hold on;
plot(x,1 + 2.77556e-17*x.^1 + -0.171088*x.^2 + 0.00530504*x.^4,'g');
% n = 6
hold on;
plot(x,1 + 2.77556e-17*x.^1 + -0.351364*x.^2 + -1.38778e-17*x.^3 
+ 0.0335319*x.^4 + 8.67362e-19*x.^5 + -0.000840633*x.^6,'b');
% n = 8
hold on;
plot(x,1 + -5.55112e-17*x.^1 + -0.528121*x.^2 + -4.16334e-17*x.^3 + 0.0981875*x.^4 
+ -5.20417e-18*x.^5 + -0.00658016*x.^6 + -1.0842e-19*x.^7 + 0.000137445*x.^8,'y');
